This solution became possible after the 1128 Battle of São Mamede, where the Portuguese barons and Archbishop of Braga, after obtaining Alfonso Henriques' active support, expelled Fernão Peres de Trava and Queen Teresa from the county.
Ultimately, given the importance of external war in forming the Peninsula's national territorial units, what likely ensured the enduring autonomy claimed at São Mamede was not the Portuguese nobility's option for Alfonso Henriques against Gelmirez or the Travas, but the sequence where they assumed the lead anti-Islamic war role, overshadowing Galician aristocracy.
True, they did not do so directly under northern lineages' intense participation and leadership, but under Alfonso Henriques' direction after he settled in Coimbra in 1131 and took an extremely active Reconquista role.